1. Field of the Invention
This invention relates to a developing device and an image forming apparatus.
2. Description of Related Art
Among image forming apparatuses of electrophotographic method, a two-component development method in which latent images formed on an image carrier are developed using a developer including toner carrier and toner, has been known. With such a two-component development method, when the toner carrier is degraded along use, the toner carrier tends to have lower charge ability. A trickle development method in which excessive developer in the developer container is discharged while new developer is supplied to the developer container (see, e.g., Japanese Application Publication (A1) No. H9-218,575), has been proposed.
With such a trickle development method, however, if new toner carrier just supplied is discharged at a time that the toner carrier is supplied, a ratio of degraded toner carrier will increase as time goes, so that the quality of the images becomes low.
It is therefore an object of the invention to provide a developing device and an image forming apparatus capable of preventing new toner carrier just supplied from being discharged.